With the continuous progresses in science and technology, LED backlight is gradually becoming a leading backlight source. Compared with the traditional CCFL backlight source, LED backlight has many advantages such as high color gamut, high luminance, long service life, energy conservation, and real-time controllable color. Especially, a high color gamut LED backlight source makes the screen of electronic products using it such as TV sets, mobile phones, and panel computers have chromatic colors and a high color reduction degree.
Currently, the common LED backlight source usually uses blue light chips to excite YAG yellow light phosphor powder. Since the backlight source lacks a red light component, the color gamut value can be up to only NTSC 65% to 72%. To further improve the color gamut value, technicians generally use blue light chips to excite both red light phosphor powder and green light phosphor powder. However, since the full width at half maximum (FWHM) of the phosphor powder used currently is large, the color gamut value of the backlight source can be increased to NTSC 80% or so, even if blue light chips are used to excite both red light phosphor powder and green light phosphor powder. In addition, considering that the excitation efficiency of current phosphor powder is low, a lot of phosphor powder needs to be used to realize high color gamut white light. As a result, the concentration (ratio of phosphor powder to packaging glue) of phosphor powder is very high during LED packaging. This greatly increases the difficulty of packaging operations and the reject ratio of products.
In recent years, attention has gradually been paid to QD materials, and especially QD phosphor powder has widely been concerned in the LED backlight industry for a series of unique optical properties, such as adjustable spectrum (as the grain size is adjusted), small FWHM of emission peak, large Stokes shift, and high excitation efficiency. Currently, QD phosphor powder is used to realize high color gamut white light in the following ways: (1) make QD phosphor powder into an optical film, fill it in a light guide panel or paste it in an LCD screen, and obtain high color gamut white light through the excitation of blue light or ultraviolet light backlight beads; (2) make QD phosphor powder into glass tubes, put them on the sides of the screen, and obtain high color gamut white light through the excitation of blue light or ultraviolet light backlight beads. However, it is very difficult for these two realization modes to realize the large-scale industrialization because of complex processes, a low photo transformation efficiency, and a high cost. For this reason, researchers have attempted to package QD phosphor powder in LED beads to obtain high color gamut white light. However, QD phosphor powder is difficult to mix with packaging glue and is easy to agglomerate to fail, and included impurities destroy packaging glue so that package glue is difficult to solidify. In view of these technical difficulties, no substantial progress has been made in the research.